Serine hydroxymethyltransferase from pyrimethamine-sensitive and -resistant strains of Plasmodium chabaudi.

Serine hydroxymethyltransferase (EC 2.1.2.1) was partially purified from a pyrimethamine sensitive strain of Plasmodium chabaudi. Km values of 2.91 and 1.08 mM were determined for tetrahydrofolate and serine, respectively. The effects of pH, of temperature and of some potential inhibitors were determined. The enzyme was also partially purified from a pyrimethamine-resistant strain of P. chabaudi and subjected to the same regime. No differences between the enzymes from the two sources could be detected. It would appear that the changes in properties in the enzymes dihydrofolate reductase and thymidylate synthetase associated with the development of drug resistance in P. chabaudi were not reflected in any obvious alterations in serine hydroxymethyltransferase.